Possible Clues:

• (Of poetry) expressing emotion
• Line of words to a song
• Song chirpily played but not hip
• With 39-Across, 21-/28-Across, for one
• Emotional student joining year one class at the beginning
• What fat ladies sing
• Poem originally conceived after year in Light Infantry
• Class put back (including Year 1) for a number of lines
• "Somewhere over the rainbow," e.g.
• Gershwin creation